Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.11.22 (cdc2)
 8,319 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

To elucidate the signal transduction mechanisms used by ligands that induce differentiation and the cessation of cell division, we utilized p13suc1-agarose, a reagent that binds p34cdc2/cdk2. By using this reagent, we identified a 78- to 90-kDa species in PC12 pheochromocytoma cells that is rapidly phosphorylated on tyrosine following treatment with the differentiation factors nerve growth factor (NGF) and fibroblast growth factor but not by the mitogens epidermal growth factor or insulin. This species, called SNT (suc-associated neurotrophic factor-induced tyrosine-phosphorylated target), was also phosphorylated on tyrosine in primary rat cortical neurons treated with the neurotrophic factors neurotrophin-3, brain-derived neurotrophic factor, and fibroblast growth factor but not in those treated with epidermal growth factor. In neuronal and fibroblast cells, where NGF can also act as a mitogen, SNT was tyrosine phosphorylated to a much greater extent during NGF-induced differentiation than during NGF-induced proliferation. SNT was phosphorylated in vitro on serine, threonine, and tyrosine in p13suc1-agarose precipitates from NGF-treated PC12 cells, indicating that this protein may be a substrate of kinase activities associated with p13suc1-p34cdc2/cdk2 complexes. In addition, SNT was associated predominantly with nuclear fractions following subcellular fractionation of NGF-treated PC12 cells. Finally, in PC12 cells, NGF-stimulated tyrosine phosphorylation of SNT was dependent on the levels of Trk tyrosine kinase activity and was constitutively induced by expression of pp60v-src. However, Ras was not required for constitutive SNT tyrosine phosphorylation, suggesting that this protein functions distally to Trk and pp60v-src but in a pathway parallel to that of Ras. SNT is the first identified specific target of differentiation factor-induced tyrosine kinase activity in neuronal cells.
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PMID:SNT, a differentiation-specific target of neurotrophic factor-induced tyrosine kinase activity in neurons and PC12 cells. 768 Nov 42

To define the molecular changes occurring in endocrine tumours, we have analysed three human endocrine tumours established in our laboratory: BON, a functioning carcinoid tumour from the pancreas; SIM, a nonfunctioning carcinoid of the ileum; and STAN, a pheochromocytoma. A homozygous point mutation of the N-ras gene was identified at codon 61 in BON cells in conjunction with overexpression of N-ras mRNA and protein. BON cells also exhibited increased expression of c-myc and cdc2 kinase mRNA and protein; TGF-beta 1, p53 and retinoblastoma (RB) mRNA and protein levels were decreased. In addition, increased expression of the mdm2 oncogene and both the truncated and the wild-type RB protein were noted in BON. SIM cells exhibited moderately increased N-ras and c-myc mRNA levels along with decreased levels of RB mRNA and protein. Similar to BON and SIM, analysis of STAN showed increased N-ras and c-myc levels. Our data show multiple molecular changes in the three human endocrine tumours with the BON cell line exhibiting the most dramatic changes. Furthermore, our data suggest the existence of different molecular pathways in the pathogenesis of endocrine tumours. These cell lines will provide unique in vitro models to further analyse the significance of these molecular alterations.
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PMID:Analysis of multiple molecular changes in human endocrine tumours. 795 99

The E6 and E7 proteins of the high risk human papillomaviruses (HPVs) are consistently expressed in HPV-positive cervical carcinomas. We investigated the ability of HPV-16 E6 and E7 to disrupt mitotic checkpoints in normal diploid human cells. Acute expression of HPV-16 E6, but not HPV-16 E7, decreased the fidelity of multiple checkpoints controlling entry into and exit from mitosis. After irradiation, nearly 50% of cells containing HPV-16 E6 readily entered mitosis as opposed to less than 10% of control cells. Consistent with this, asynchronous populations of cells expressing HPV-16 E6 had increased cdc2-associated histone H1 kinase activity relative to control populations. In addition, HPV-16 E6 increased sensitivity to chemically-induced S-phase premature mitosis and decreased mitotic spindle assembly checkpoint function relative to control populations. HPV-16 E6 mutants with a reduced ability to target p53 for degradation were unable to abrogate mitotic checkpoints, suggesting a possible mechanism by which HPV-16 E6 disrupts mitotic checkpoints. Expression of a mutant p53 gene yielded an intermediate phenotype relative to HPV-16 E6, generating moderate increases in sensitivity to chemically-induced S-phase PCC and mitotic spindle disruption and a heightened propensity to enter mitosis after irradiation.
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PMID:The human papillomavirus-16 E6 oncoprotein decreases the vigilance of mitotic checkpoints. 944 51

Bailie et al. [In Vitro Cell Dev. Biol. (1992) 28A, 621-624] reported that primary cultures of rat hepatocytes possess low affinity binding sites for nerve growth factor (NGF). NGF treatment of primary cultures of rat hepatocytes with a maximally effective concentration of NGF (20 ng/ml, 0.8 nM) caused acute phasic activation of Raf-1 and p42(MAPkinase), and a smaller sustained activation of B-Raf. The transient increase in Raf-1 and p42(MAPkinase) activity returned to baseline within approximately 30 min. NGF treatment of hepatocytes did not induce expression of cyclin dependent kinase (cdk) inhibitor proteins, but instead stimulated cdk2 activity and increased [3H]thymidine incorporation into DNA. In contrast to hepatocytes, NGF treatment of PC12 pheochromocytoma cells caused large sustained activations of B-Raf and p42(MAPkinase), and a lower phasic activation of Raf-1. The sustained activations of B-Raf and p42(MAPkinase) were for more than 5 h. Treatment of PC12 cells with NGF increased p21(Cip1/WAF-1) expression, reduced cdk2 activity and inhibited DNA synthesis, the opposite to the effects of NGF treatment of hepatocytes. However when p42(MAPkinase) was chronically activated in hepatocytes, via infection with an inducible oestrogen receptor-Raf-1 fusion protein, expression of p21(Cip-1/WAF1) and p16(INK4a) cdk inhibitor proteins increased, cdk2 activity decreased, and DNA synthesis decreased. Equally, treatment of hepatocytes with 50 mM ethanol elevated the basal activity of p42(MAPkinase) and temporally extended the ability of NGF treatment to activate p42(MAPkinase). Ethanol and NGF co-treatment increased expression of p21(Cip-1/WAF1) and p16(INK4a) cdk inhibitor proteins and decreased hepatocyte DNA synthesis. These data demonstrate that NGF can cause either acute/phasic or sustained activation of the MAP kinase cascade in different cell types. Acute activation of the MAP kinase cascade correlated with increased DNA synthesis. In contrast, sustained activation of the MAP kinase cascade correlated with increased expression of cdk inhibitor proteins, a reduction in cdk activity, and an inhibition of DNA synthesis. These data suggest a general mechanism exists where acute activation of the MAP kinase cascade promotes G1 progression/S phase entry and that chronic activation of the MAP kinase cascade inhibits this process.
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PMID:The mitogen-activated protein (MAP) kinase cascade can either stimulate or inhibit DNA synthesis in primary cultures of rat hepatocytes depending upon whether its activation is acute/phasic or chronic. 949 19

The involvement of cdc2 and cdk2 during neuronal differentiation in rat pheochromocytoma PC12 cells was examined. When PC12 cells were cultured with nerve growth factor (NGF), expression of cdc2 decreased significantly after day 5, while expression of cdk2 decreased gradually after day 7. Cells overexpressing cdc2 or cdk2 were resistant to NGF-induced differentiation and growth suppression, and maintained high cdc2 or cdk2 kinase activity, respectively, during NGF treatment. In contrast, the NGF-treated parental cells showed a marked decline in these kinase activities after day 3. When PC12 cells were treated with specific inhibitors of cdc2/cdk2 (butyrolactone-I, olomoucin), they showed marked neurite extension and up-regulation of microtubule-associated protein 2 expression. In addition, treatment with mixtures of antisense oligonucleotides for cdc2 and cdk2 resulted in down-regulation of both cdc2 and cdk2 kinase activities as well as significant neurite outgrowth and up-regulation of microtubule-associated protein 2 expression. However, neurite outgrowth was not observed in cells treated with either single antisense oligonucleotide, or antisense cdc2 + cdk4 or cdk2 + cdk4 oligonucleotide mixtures. These results suggest that simultaneous down-regulation of cdc2 and cdk2 activity is sufficient and necessary for neuronal differentiation in PC12 cells.
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PMID:Simultaneous suppression of cdc2 and cdk2 activities induces neuronal differentiation of PC12 cells. 1077 47

The induction of apoptosis by cell cycle regulator molecules under conditions optimal for exponential growth was examined in rat pheochromocytoma PC12 cells by overexpression of cyclins and cyclin-dependent kinases (cdks). By flow cytometry and by immunofluorescence, only cells overexpressing cdk4 or cyclin D1 underwent apoptosis, which was not associated with G1-arrest. Cdk4 kinase activity was significantly higher in cdk4-, or cyclin D1-expressing cells. Furthermore, induction of apoptosis by cdk4 was abrogated by co-transfection of p16(INK4), or dominant negative cdk4. These results suggest that upregulation of cdk4 kinase activity is a primary and critical mediator of apoptosis in PC12 cells under physiological conditions.
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PMID:Overexpression of cdk4/cyclin D1 induces apoptosis in PC12 cells in the presence of trophic support. 1174 60

The aim of this study was to identify key genes whose expression is altered by heme and heme deficiency in the human erythroleukemia K562 cells and in the NGF-induced rat pheochromocytoma neuronal PC12 cells, respectively. By quantitative RT-PCR, Northern blotting, and Western blotting analyses, we found that the expression of the CDK inhibitors p18 and p21 was upregulated at the early and late stages of heme-induced erythroid differentiation of K562 cells, respectively, while the expression of cyclin D1 was downregulated. Data from succinyl acetone and desferrioxamine treatments suggest that these effects of heme in K562 cells were specific. Further, by microarray expression analysis, we found that inhibition of heme synthesis by succinyl acetone in NGF-induced PC12 cells drastically altered the expression of several groups of important neuronal genes, including the structural genes encoding neurofilament proteins and synaptic vesicle proteins, regulatory genes encoding signaling components beta-arrestin and p38 MAPK, and stress-response genes encoding hsp70. These results show that heme and heme deficiency affect the expression of diverse genes in a cell-type specific manner in mammalian cells, and that heme, although needed at different levels, is critical for both erythropoiesis and neurogenesis. These studies provide insights into how heme may act to control diverse regulatory processes in mammals.
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PMID:An examination of heme action in gene expression: heme and heme deficiency affect the expression of diverse genes in erythroid k562 and neuronal PC12 cells. 1204 72

Rad9 is required for the activity of the genotoxin-induced checkpoint signaling pathway to control cell cycle progress and maintain genomic stability. In the fission yeast S. Pombe and chicken cells, the Rad9 gene is essential for prevention of premature chromosomal condensation (PCC:S/M checkpoint control). However, precise features in the S/M checkpoint controlled by Rad9 in mammalian cells are still not clear. In this study, mouse embryonic stem (ES) cells with a targeted deletion of Mrad9, the counterpart of S. pombe rad9, were used to evaluate the detailed function of Mrad9 in S/M checkpoint control. We found that Mrad9 deletion from ES cells led to failure of S/M checkpoint control across the entire S phase, and was alleviated by introducing mouse or human Rad9 into the Mrad9-deleted cells. We also found that the phosphorylation sites on Tyr28 and the C-terminus of Rad9 are required for this checkpoint control. Moreover, the DNA replication inhibitor hydroxyurea (HU) induced cdc2 Tyr15 phosphorylation and increased 14-3-3sigma protein levels in Mrad9(+)/(+) ES cells, but failed to do so in Mrad9(-)/(-) ES cells. Taken together, these results suggest that phosphorylation of Rad9 plays a critical role in the activation of the S/M checkpoint, and that downstream proteins cdc2 and 14-3-3sigma mediate this function.
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PMID:Phosphorylation sites on Tyr28 and the C-terminus of Rad9 are required for inhibition of premature chromosomal condensation across the entire S phase. 1876 57

The activity of the dual specificity phosphatase cdc25C is required for mitotic progression though the mechanisms by which cdc25C is activated prior to mitosis in human cells remain unclear. The data presented herein show that the actin binding protein Filamin A forms a complex with cdc25C in vivo and binds preferentially to the mitotic form of cdc25C. Co-expression of Filamin A with cdc25C results in an increase in PCC induced by cdc25C, while knocking down Filamin A expression reduces the levels of PCC induced by cdc25C overexpression. Further, only a Filamin A fragment that forms a complex with both cdc25C and cyclin B1 and retains the dimerization domain can stimulate the ability of cdc25C to induce PCC. These results suggest that Filamin A provides a platform for the assembly of the cyclin B1-cdk1- cdc25C complex resulting in cdk1 activation and mitotic progression.
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PMID:Filamin A stimulates cdc25C function and promotes entry into mitosis. 2132 83